Process for preparing nitriles

ABSTRACT

A process for the production of a nitrile having three to 12 carbon atoms per molecule by contacting at a temperature of 400* to 500* C and a contact time of 10 to 0.1 seconds a gaseous mixture of hydrocarbons of three to 12 carbon atoms containing the group AND AMMONIA WITH AN IRON AND ARSENIC CONTAINING CATALYST HAVING AN ATOMIC RATIO OF IRON TO ARSENIC OF 1.1:1 TO 10:1 PREPARED BY ADDING AN AQUEOUS ARSENATE SALT SOLUTION TO AN AQUEOUS FERRIC SALT SOLUTION, ADJUSTING, THE PH value of the resulting solution to between 0.5 and 6, evaporating and calcining the product.

United States Patent Huibers et al.

[151 3,699,147 [451 Oct. 17,1972

1541 PROCESS FOR PREPARING NITRILES [72] lnventors: Derk Th. A. l'luibers, Berkeley Heights; John J. Waller, Jersey City, both of NJ.

The Lummus Company, New York, NY.

[22] Filed: April 4, 1969 [21] Appl. No.: 844,684

Related U.S. Application Data [62 Division of Ser. No. 548,396, May 9, 1966, Pat.

[73] Assignee:

[52] U.S. Cl ..260/465 C, 260/465.3, 260/603 HF,

260/668 D, 260/680 E, 260/680 R, 260/683 [51] Int.Cl ..C07c 121/02,C07c121/32, I C07c 121/50 [58] Field of Search ..260/465 C, 465.3

[56] References Cited UNITED STATES PATENTS 3,478,082 11/1969 Huibers et al. ..260/465.3

FOREIGN PATENTS OR APPLICATIONS I 999,629 7/1965 Great Britain Primary Examiner-Joseph Rebold I Assistant Examiner--D0lph l-l. Torrence I Att0rney--Richard .1. Bolton [57] 7 ABSTRACT and ammonia with an iron and arsenic containing catalyst having an atomic ratio of iron to arsenic 'of 1.1:1 to 10:1 prepared by adding an aqueous arsenate salt solution to an aqueous ferric salt solution, adjusting, the pH value of the resulting solution to between 0.5 and 6,- evaporating and calcining the product.

8 Claims, No Drawings saturated nitriles such as acrylonitrile has been identified as ammoniation. Similarly, when the olefin-ammonia charge also includes an active oxygencontaining gas such as air, the reaction has been designated ammoxidation.

' A number of catalyst compositions have been proposed and some have been used in ammoniation and ammoxidation operations. While some are effective, they are not wholly satisfactory with respect to selective conversion of olefin to the corresponding unsaturated nitrile. Generally, substantial-quantities of olefin are consumed in less desirable or undesirable side reactions. Then, too, some of the catalysts have limited activity and useful life. A further shortcoming is the relatively low yield of desired product per unit weight of catalyst per hour of on-stream time. Finally, the presently used catalysts are costly because their ingredients are in short supply. I

For example, antimony oxide-iron oxide catalysts have been described for use in ammoxidation of olefins a. adding an aqueous solution of an arsenate salt to an aqueous solution of a ferric salt,

b. adjusting the pH of the resulting solution with sufficient base to maintain the pH thereof between about 0.5 and about 6,

c. evaporating the resulting solution of (b), and

d. calcining the product of (c), thereby obtaining said catalyst having an atomic ratio of iron to arsenic (Fe/As) from about 0.1:1 to about :1, and preferably 0.5:1 to 1.521.

In accordance with the present inventiomthere are also provided novel catalysts, particularly catalysts prepared by the process described above.

Another embodiment of the present invention comprises the process for the production. of nitriles having from three to about 12 carbon atoms per molecule,

which comprises contacting, at a temperature between to nitriles, particularly propylene to acrylonitrile.

While substantial conversion of propylene to the desired nitrile is realized with the antimony-iron catalysts, considerable loss results with the formation of carbon oxides and other by-products. Selectivity, then, is subject to improvement. Similarly, the yield of acrylonitrile perunit weight of catalyst is also subject to improvement.

Arsenicand iron-containing catalyst compositions are also known for reactions other than ammoniation and ammoxidation. By way of illustration, iron arsenite and iron arsenates are described for converting aldehydes to nitriles using ammonia and oxygen. Such catalysts have been found to have little activity for the reactions of propylene-ammonia and propylene-ammonia-oxygen to form acrylonitrile.

The present invention is predicated upon discovery of new arsenicand iron-catalysts having substantial selectivity and activity for ammoniation and ammoxidation, and of a process for preparing the catalysts.

It is an object of the present invention, therefore, to provide new catalyst compositions. Another object is to provide catalysts having excellent catalytic activity and/or catalytic selectivity. A further object is to proabout 400 C. and about 500 C. and a contact time from about 0.1 second to about 10 seconds, a gaseous mixture comprising certain unsaturated hydrocarbons having from three to about .12 carbon atoms per molecule and ammonia in the presence of a catalyst formed by the process described above. Still another embodiment involves a related ammoxidationprocess in which the gaseous charge mixtureincludes an active oxygen-containing gas.

As indicated above, the catalysts of this invention are prepared by adding an aqueous solution of an arsenate salt to an aqueous ferric salt solution, while thoroughly agitating the same. The arsenate can be an alkali metal salt, alkaline earth metal salt or ammonium salt including (NI-[0 H AsO (NH,,)H AsO, and (NH AsO .3 H O. Ammonium salts are preferred. Correspondingly, a variety of ferric salts are contemplated. The ferric salts include: nitrate, chloride, acetate and sulfate;

N QQQHZQ$2593???- E sm aPQPL qabcu 10 molar proportions of arsenate are generally used for each molar proportion of ferric salt, such that the final catalyst composition has an arsenic content and an iron content as expressed above in (c).

In addition to using aqueous arsenate and aqueous ferric salt solutions, it has been found that certain solvents can also be included to advantage. The solvents provide maximum atomic contact of ironand arseniccontaining components in the preparation of the catalysts, and effect the porosity of the catalysts. The solvents are nitrogen-containing compounds having a solubility in water of at least about 5 percent by volume. Typical of such solvents are dimethyl formamide, acetamide, methylamine, diethanolamine, and acetonitrile.

It has been found that the order of addition is important for the production of the desired catalyst. When a clear aqueous ammonium arsenate solution (pH, 4.0) is added with agitation to a clear ferric nitrate solution (pH, 0.5), no precipitate is formed. Whereas, upon reversal of the order of addition, it was surprisingly found that a ferric hydroxide-containing precipitate is formed: this precipitate does not readily go into solution again during the preparation. Further, by proceeding with the preparation following production of this precipitate, by evaporating water and ammonia and subsequently calcining, a composition differing from the desired catalytic composition is produced because iron and arsenic moities exist separately.

After the arsenate solution has been added to the ferric salt solution, alkali preferably aqueous ammonia is added to the resulting solution in order to control pH of the latter. Other alkaline materialswhich can be used include lower. aliphatic amines, NaOH KOH, Ba(OI-l) and.Ca( ()l-l) Surprisingly; when the pH is below about 0.5 andabove about 6, the'final catalytic compositions have substantially lower activity than do those formed with a pH at this stage within the approximate range of 0.5-6. Preferably, the pH ranges from about 1 to about 4, and especiallyv about 4.

Following adjustment of pH, the resulting product is evaporated in order to remove water and free ammonia therefrom. Generally, this can be accomplished by heating to from about 50 C. to about 105 C. fora suitable period of time. Upon evaporation, a solid mass is formed. The mass is crushed or pulverized to size as about 20 mesh, by conventional means, and the resulting particles are then calcined. Alternatively, the mass may be calcined directly. The particles are calcined conveniently in a furnace at 450 C. for 2 hours; however, temperatures from 400 C. to 700 C. can be used for'tirne intervals of 10 hours to 0.5 hour. The temperature should be increased slowly in order to obtain catalysts having a high order of activity.

The catalyst compositions per se can be used or they can be used inconjunction with :known supports and extenders in conventional manner. Thus, they can be 'mixed withsilica,,.diatomaceous earth, pumice, clays Hydrocarbonsused herein for the formation of.

nitriles have from threetoab'out 12 carbon atoms per molecule and have thecharacterizing group Thus,:a methyl group a trigonal carbon cluded in the charge. Temperatures ranging from about 400 C. to 500 C. are used, with residence times of 10 seconds to 0.1 second. Preferred conditions are 425-475 C.,. and 4 seconds to 1 second. 7

Reaction conditions for ammoxidation are substantially the same'as those given directly above. However, an active oxygen-containing gas is also charged. Gases include oxygen, oxygen-steam mixtures and oxygennitrogen mixtures such as air, withthe last-mentioned preferred. Molar ratios of ammonia to oxygen are 5:1 to 05:1, and of'olefin to oxygen 5:1 to 05:1. Oxygen serves to maintain the catalytic activity of the catalyst compositions, obviating or lessening the need to remove and separately reoxidize them.

The catalysts can be reactivated when heated in the air, at a temperature of from about 350 C. to about 700 C.

The invention is illustrated by the following examples.

The reactor used in several of the illustrative examples comprises a inch inside diameter tube confined in a furnace which is heated electrically. A preheater' section-of the tube is filled with inert material, such as carborundum. A- reactor section of the tube is filled with catalyst. Gases charged to. the reactor are passed through rotameters. The exit line from the reactor is maintained at about 110 C. A sample valve is maintained at 110 C. Product gas samples are analyzed in a gas chromatograph, using a diethylhexyl sebacate, 60

'80 diaport S column (8 feet X V4 inch) at C. wit carrier gas (helium) flowrate of 40 cc/min.

EXAMPLE 1 Anhydrousammonium'arsenate (39.8 grams)vwas dissolved in '200 milliliters. (ml) of distilled water. The solution so obtained was added to and mixed with a solution of 80.8 g. of ferric nitrate nonanhydrate in 200 ml of water; Concentrated aqueous ammonia was then added to provide a pH of 4.1. The resulting solution was evaporated at 50 C. The solid obtained .by evaporation was crushed to size (20 mesh) and was calcined in a tube furnace at 450 C. for 2 hours. The catalyst has a composition represented by mo, As O It is a hard yellow solidhaving a bulk density of 0.59. g

EXAMPLE 2 The procedure of Example. 1 was followed except for dissolving the arsenate in 200 ml of dimethyl formamide and 520 ml of distilled water, before the resulting solution was added to the ferricnitrate solution. The catalyst obtained was yellow ochre incolor, has a bulk density of 0.40 and has the form Fe 0 .As O

The new catalytic compositions are effective for am moniation and ammoxidation, asshown'in the following illustrative examples. Comparative examples are also included to demonstrate advantages over related compositions. I

EXAMPLE 3 (A) A catalyst, prepared as in EXAMPLE 1, but with a pH of 1, was charged to thereactor and, brought to 460 C. with a nitrogen purge. The quantity of catalyst was 9 grams (10ml). A gaseous mixture of percent nitrogen, 15 percent propylene and 10 percent ammonia (by volume) was charged to the reactor at a rate of 244 cc/rninute. The effluent gas initially produced contained 2.72 percent by volume of acrylonitrile and 0.05 percent by volume of acetonitrile. The conversion to acrylonitrile isthus about 18 percenton propylene and 27 percent on ammonia and the selectivity ratio is 98 percent. The space yield is 1 14 g. of acrylonitrile per kilogram of catalyst per hours. (B) By way of comparison, the procedure described in (A) was repeated except for operation at 465 C. and a different catalyst. The catalyst was the same as that which is described in EXAMPLE 1, above, except for presence of anactive oxygen-containing gas, such as adjustment of pH to 7 during its preparation.

The effluent gas initially produced contained 0.57 percent by volume of acrylonitrile, 0.015 percent by volume of acetonitrile and 0.052 percent by volume of HCN. Accordingly, conversion .to acrylonitrile-is about -6 AzReactorFeed A comprising (at 20 C., ml/min.) N2, can NH3 total ml/min.

B: Reactor Feed B at 20 C., ml/min.)

9" f f and -7P 2 5 59.1 air, 5.3 c 11, 5.8 NH, total 31.3 mI/min. The selectivity ratio is about 90 percent and space yield D is 27 grams of acrylonitrile per kilogram of catalyst per Acrylommle hour. AcN: Acetonitrile TABLE 1 Conversion to Resl- I Ncontain1ng Selectivity (percent) dence products Time, Products, mL/mln. AN, Space, yield, Catalyst Temp sec. C1130, NHa, AN total g. AN, kg. No. Grams "0 Charge AN AcN HGN Total percent percent AN ACN1 N-prod. cat/hr.

5.9 459 2 A- 3.55 0.21 3.01 30.0 45.9 1 91 91 80, 5.9 10 450 3 B 4.12 0.21 4.93 85.0 35.0 95 95 100 4 10 45s 2 A 2.33 0.10 0 054 2.54- 21.2 31.8 1 94 92 11 4 10 449 3 B 2.50 0.24 2.94 49.0 49.0 -92 92 86 3.0 10 v403 2 'A' 2.09 0.078 0.013 2.19 19.2 21.3 95 93 11 Comparative Exampl 1.4 10 401 2 A 2.10 0.115 2.82 23.5 35.2 90 95' 48 1.0 10 450 3 B 1.80 0.054 1.86 32.0 32.0 91 91 34 0.4 10 408 2 A 2.39 0.39 0 021 2.19 23.3 34.9 35 85 49 0.4 '10 449 3 B 2.90 0.15 3.05 52.5 52.5 95 95 00 10 10 458 2 A 2.81 0.052 2.91 23.9 35.9 1 9s 98 31 10 10 44s 3 B 1.33 0.114 0.018 1.95 33.8 33.3 94 .93 24 (C) An ironand arsenic-containing catalyst formed CATALYST COMPOSITIONS in a strong acid medium was also compared with the :v o f l d catalysts of this invention. The procedure of 3 (A) Z 0 e F6203 AS605 A Justed above, wasfollowed with the same charge and charge 11 :Pm du ct of EX 8 m p162 Fezoa A52 0, rate. Reaction temperature was 464 C. and residence 3 12 F 0 A O t t d time about 1 second. The quantity of catalyst was 7.5 p' Z S2 5 7 P (w .Juste grams (l0 ml).*The effluent gas initially produced contained 0.05 8 percent by volume of acrylonitrile. Conf- A gzd rfi NOaadded in orig version to acrylonitrile was about 0.4 percent on 14 zf gd propylene and 0.6 percent on ammonia. Space yield is 3 2.6 grams of acrylonitrile per kilogram of catalyst per hour.

This iron-arsenic catalyst was preparedby dissolving 55.9 g. of iron in a mixture of 250ml. of nitric acid (density, 1.4) andx500-ml. of water at 90-95 C. An aqueous solution (188.4'g) of arsenic oxide,60 percent by weight, was added thereto. The resulting mixture was evaporated to dryness in an oven at 110 C. The residue was calcined at 450 C. for 24 hours. The mass so obtained was [finely ground, homogenized and formed into pastilles.

EXAMPLE 4 The catalyst of EXAMPLE 3(A) was used. Tl-le reactor was charged with 3.9 grams (4.4 ml) of .the catalyst. The catalyst was heated to 440 C. with a nitrogen stream passed over it. A gaseous mixture was charged to the reactor at the rates indicated: 89 percent N 11 percent 0 300 cc/minute; ammonia, 20 cc/minute and propylene, 20 cc/minute. The effluent gas from the-reactor contained 1.23 percent by volume of acrylonitrile and 0.10 percent by volume of acetonitrile. The conversion to acrylonitrile is thus about 21 percent on both propylene and ammonia and the selectivity ratio is 93 percent. The space yield is 140 grams of acrylonitrile per kilogram of catalyst per hour.

. In Table 1 following, a series of illustrative examples is provided. The reactor referred to in Examples 3 and 4 was employed and the procedure thereof was followed. 1n the Table, the following symbols are used to represent:

l5 Fe; 03 05 I I It is to be noted that with Feed B the space; yield value was 60 with Catalyst Composition 14 in comparison with values of 106 and 86for'Catalyst Compositions 10 and 11, respectively, under comparable conditions. Further, conversion of propylene was percent with Catalyst Composition 10 as opposed to 52.5 percent with Catalyst Composition l4.

EXAMPLE 5 Methacrylonitrile was prepared in the absence of oxygen from isobutene and ammonia. The catalyst used was Fe O As; 0 similar to that of EXAMPLE 3(A), but with a lower bulk density. Ten 10) milliliters, 10 grams, of the catalyst were used in the reactor following the procedure of EXAMPLE 3(A). Reaction temperature was 452 C. Residence time was about 1 second, with a charge containing isobutene in place of propylene. The charge comprised 36.6 ml/min. of isobutene, 24.4 ml/min. of ammonia and 183 ml/min. of nitrogen. v

The effluent gas initially produced contained, by volume: 0.67 percent methacrylonitrile; 0.58 percent acrylonitrile and 0.03 percent acetonitrile. Conversion to nitrogen-containing products is about 8.5 percent on EXAMPLE 5 In an ammoxidation procedure, acrylonitrile was formed in larger quantity than methacrylonitrile from isobutene. Thev procedure-of EXAMPLE was followed withthe feed also comprising 18 ml. of air per minute. Reactiontemperature was 460 C. Residence time was about 0.93 second.

' Corresponding results were: 0.23 percent methacrylonitrile; 1.69 percent acrylonitrile and 0.01 percent acetonitrile. Conversion to nitrogen-containing,

products is -'l'3.8-'per'cent onisobutene and 20.8 percent on ammonia, Space yields of methacrylonitrile and acrylonitrile, respectively, were 14 and 811 grams per kilogram of catalystper ho'ur. I

. EXAMPLE 7 p-Xylene was converted to terephthalonitrile (TPN). Charged to the reactor were: 1 24 ml/mimof ammonia,

0.53 mllmin. water and 0.1 ml/min. of p-xylene. The catalyst quantity :was 131.3 grams (200 'ml). The catalyst is Catalyst Composition No. 10 of the Table catalyst compositions .in the form of their oxides or salts, typical of which are sulfates,,chlorides, nitratesgiven in EXAMPLE 4, above. 'It has'a bulk density of 0.657 g/rnl. Reaction temperature was 460 C. and contact time 0.56tsecond; Space yield of TPN was-6.1

grams per kilogram of catalyst per hour.

It isapparent 'from comparative examples 1 given above that the catalysts of this invention are not only more active'but more selective than related catalysts, since they provid eessentially the same yields at high conversion'as the related catalysts provide at'low conversions. r a

As indicated above, the catalyst compositions of this invention are characterized by oxides of iron and arsenic 'such that the; atomic ratio of iron to arsenic (Fe/As) is from about 0.121 to 10:1 and'preferably 0.5:1 to 1.521. Iron and arsenic are molecularly dispersed in the composition, which are generally yellow in color.

The catalyst compositions of this invention can beused for reactions in addition to those indicated above. For example, they can be used for dehydrogenation of hydrocarbons as illustrated by dehydrogenation under 3 known dehydrogenation reaction conditions of temperature and pressure. Temperatures of 400-600 C.' i and pressure of. l 5 atmosphere's'are typical. Ethylbenzene can be converted to styrene and butenes to butadiene. Oxygen may be added to the hydrocarbon charge in such dehydrogenations'These reactions can i be carried out in the presence or absence of molecular oxygen, and for diluents such as nitrogen or steam.

In another use, these catalysts were used in the air oxidation of methanol to formaldehyde.

Activity and/or selectivity of the new catalyst compositions can be enhanced by incorporation of one or more promoters therein. From about 2 to about 10 percent by weight, based upon the ironand arsenic-conwith such components.

taining composition, of promoter can be used. As contemplated herein, the promoters include the following:

atoms in which aninner d level'is present but not filled to capacity. Thesemetals are illustratedby bismuth, tin, platinum, cobalt, nickel,.vanadium, chromium, titanium, zirconium, molybdenum tungsten and lead.

The metals can be added during the preparation of the and acetates. v j

2. Alkali metals, alkaline earth metals including magnesium, and aluminum, added in the form of their hydroxides or salts. Selectivity is particularly promoted 3. Acids including. bori'c', fluoboric, phosphoric, antimonic and halogen acids can be added during the catalyst preparation. The acids particularly increase catalyst activity.

What is claimed is:

1. The process for the=production of a nitrile having from three to about 12 carbon atoms per molecule, which'comprises contacting at atemperature' between about 400 C and about 5009 C and a contact time from about 10 second to about 0.1 second a gaseous mixture comprising a hydrocarbon having from three to about 12 carbon atoms per. molecule and having at least one methyl group attached; to a trigonal carbon atom and ammonia in a molar ratio of hydrocarbon toammonia of 0.5:1 to 2:1 per methyl group,.in the presence of a catalyst formed by (a) adding an aqueousars'enate salt solution to an aqueous ferric salt'solution, (b) adjusting the pH of the resulting solution to between about 0.5

and 6, (c) evaporating the resulting solution of (b), and (d) calcining the product of (c), the quantities of the arsenate salt and the ferric salt being so chosen that a catalyst having an atomic ratio of iron to arsenic from 0 l:1,to 10:1 is obtained, wherein the rsenate salt is an alkali metal arsenate,an alkaline ea metal arsenate,

methacrylonitrile and the hydrocarbon is isobutene.

8. The process of claim 5 wherein the nitrile is. terephthalonitrile and the hydrocarbon is p-xylene.

1. Transition metals which are characterized by 

2. The process of claim 1 wherein the nitrile is acrylonitrile and the hydrocarbon is propylene.
 3. The process of claim 1 wherein the nitrile is methacrylonitrile and the hydrocarbon is isobutene.
 4. The process of claim 1 wherein the nitrile is terephthalonitrile and the hydrocarbon is p-xylene.
 5. The process of claim 1 wherein the gaseous mixture contains an active oxygen-containing gas.
 6. The process of claim 5 wherein the nitrile is acrylonitrile and the hydrocarbon is propylene.
 7. The process of claim 5 wherein the nitrile is methacrylonitrile and the hydrocarbon is isobutene.
 8. The process of claim 5 wherein the nitrile is terephthalonitrile and the hydrocarbon is p-xylene. 